Master, transfer copy, and method for manufacturing master

ABSTRACT

There are provided a master and a method for manufacturing the master, the master having, on its outer peripheral surface, a concave-convex structure in which concavities or convexities are continuously arranged with high precision. The master includes: a substrate with a hollow cylindrical shape or cylindrical shape; and a concave-convex structure on an outer peripheral surface of the substrate. The concave-convex structure has concavities or convexities continuously arranged at a predetermined pitch in a circumferential direction of the substrate. The concavities or convexities are arranged with a predetermined phase difference between circumferential rows adjacent in an axial direction of the substrate.

CROSS REFERENCE TO PRIOR APPLICATION

This application is a divisional of U.S. patent application Ser. No.16/332,464 (filed on Mar. 12, 2019), which is a National Stage PatentApplication of PCT International Patent Application No.PCT/JP2017/031991 (filed on Sep. 5, 2017) under 35 U.S.C. §371, whichclaims priority to Japanese Patent Application No. 2016-181844 (filed onSep. 16, 2016), which are all hereby incorporated by reference in theirentirety.

Technical Field

The present invention relates to a master, a transfer copy, and a methodfor manufacturing the master.

BACKGROUND ART

Imprinting is one of micro-processing techniques that have been recentlydeveloped. In imprinting, a cylindrical master having a fineconcave-convex structure on its surface is pressed against a resin sheetor the like so that the concave-convex structure on the surface of themaster is transferred to the resin sheet.

The master used in imprinting is manufactured by using, for example,laser lithography. Specifically, the master is manufactured bycontinuously forming a pattern on the outer peripheral surface of acylindrical substrate by irradiation of the substrate with a laser beamwhile the cylindrical substrate is rotated about its central axis andscanning is performed in the axial direction of the substrate.

Here, there is a need to further improve processing precision ofimprinting like other micro-processing techniques. In particular, when atransfer copy having a concave-convex structure is used as an opticalmember such as an anti-reflection film, there is a need to increase thedensity of concavities or convexities and precisely control thearrangement of concavities or convexities in order to reduce diffractionand scattering and improve optical characteristics. There is also a needto precisely control the arrangement of a concave-convex structure onthe transfer copy for surface plasmon filters and substrates forlight-emitting devices.

There is therefore a need of a technique for more precisely controllingthe arrangement of an exposure pattern on the outer peripheral surfaceof a cylindrical master used in imprinting.

For example, Patent Literature 1 described blow discloses a nanoimprintmold exposure method. In this method, the exposure start position iscontrolled on the basis of a start pulse of a rotation control signalwhen an exposure pattern is formed on a roll-shaped member. In thetechnique disclosed in Patent Literature 1, an exposure pattern with adesired arrangement is obtained by controlling the start position of theexposure pattern for each rotation of the roll-shaped member on thebasis of a start pulse generated at regular timing for each rotation ofthe roll-shaped member.

CITATION LIST Patent Literature

Patent Literature 1: JP 2011-118049 A

SUMMARY OF INVENTION Technical Problem

However, the technique disclosed in Patent Literature 1 described abovefails to provide the continuity of the exposure pattern since the startposition of the exposure pattern is controlled for each rotation of theroll-shaped member. As a result, the exposure pattern on the roll-shapedmember has a blank region with no exposure pattern at one position foreach rotation. In the technique disclosed in Patent Literature 1, it isthus difficult to form a continuous exposure pattern withoutinterruption on the outer peripheral surface of the roll-shaped memberwhile controlling the arrangement of the exposure pattern.

Accordingly, the present invention has been devised in light of theabove issue, and an object of the present invention is to provide anovel and improved master having, on its outer peripheral surface, aconcave-convex structure in which the arrangement of concavities orconvexities is precisely controlled, a transfer copy obtained by usingthe master, and a method for manufacturing the master.

Solution to Problem

To solve the problem described above, according to an aspect of thepresent invention, there is provided a master including: a substratewith a hollow cylindrical shape or cylindrical shape; and aconcave-convex structure on an outer peripheral surface of thesubstrate. The concave-convex structure has concavities or convexitiescontinuously arranged at a predetermined pitch in a circumferentialdirection of the substrate. The concavities or convexities are arrangedwith a predetermined phase difference between circumferential rowsadjacent in an axial direction of the substrate.

It is preferable that the concave-convex structure do not have a blankregion where the concavities or convexities are not formed in the axialdirection of the substrate, or an error region where concavities orconvexities are formed in an arrangement different from the arrangementof the concavities or convexities.

The concave-convex structure may have the concavities or convexitiesarranged in a hexagonal lattice.

An average pitch between the concavities or convexities may be less than1 μ.

At least the outer peripheral surface of the substrate may include aglass material.

To solve the problem described above, according to another aspect of thepresent invention, there is provided a method for manufacturing amaster, the method including: a step of sharing a reference clockbetween a plurality of signal generating circuits, and generating arotation control signal and an exposure signal in the plurality ofrespective signal generating circuits; and a step of forming a patternon an outer peripheral surface of a substrate with a hollow cylindricalshape or cylindrical shape by rotating the substrate about a centralaxis of the substrate on a basis of the rotation control signal andirradiating the outer peripheral surface of the substrate with a laserbeam on a basis of the exposure signal while performing scanning in anaxial direction of the substrate.

It is preferable that a frequency of the rotation control signal be notan integral multiple of a frequency of the exposure signal.

It is preferable that, in one rotation of the substrate, a number ofpulses from the rotation control signal be an integer, and a number ofpulses from the exposure signal be not an integer.

The rotation control signal may be in synchronization with the exposuresignal.

The outer peripheral surface of the substrate may be provided with aresist layer to be patterned by irradiation with the laser beam. Themethod may further include a step of forming a concave-convex structureon the outer peripheral surface of the substrate by etching thesubstrate using, as a mask, the resist layer that has been patterned byirradiation with the laser beam.

The patterning by irradiation with the laser beam may be performed bythermal lithography.

To solve the problem described above, according to another aspect of thepresent invention, there is provided a master manufactured by the methodaccording to any one of what have been described above.

To solve the problem described above, according to another aspect of thepresent invention, there is provided a transfer copy obtained bytransferring a concave-convex structure on an outer peripheral surfaceof the master to a sheet-shaped substrate with the master.

Advantageous Effects of Invention

According to the present invention as described above, it is possible toprovide a master having, on its outer peripheral surface, aconcave-convex structure in which the arrangement of concavities orconvexities is precisely controlled. It is also provide a transfer copyto which the inverted structure of the concave-convex structure on theouter peripheral surface of the master has been transferred.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic perspective view of a master according to anembodiment of the present invention.

FIG. 2 is a plan view of an example of a concave-convex structure on anouter peripheral surface of the master according to the embodiment.

FIG. 3 is a schematic view illustrating an exposure method used in amethod for manufacturing a master according to an embodiment of thepresent invention.

FIG. 4 is an explanatory view illustrating a correspondence relationshipbetween an exposure signal and an exposure pattern in the embodiment.

FIG. 5 is an explanatory view illustrating a correspondence relationshipbetween the exposure signal and a rotation control signal in theembodiment.

FIG. 6 is a block diagram illustrating a mechanism for generating theexposure signal and the rotation control signal in the embodiment.

FIG. 7 is a block diagram describing a specific configuration of anexposure apparatus used in exposure of a substrate in the embodiment.

FIG. 8 is a schematic view illustrating a configuration of a transferapparatus for manufacturing a transfer copy by using a master accordingto an embodiment of the present invention.

FIG. 9 is a SEM image of a transfer copy according to Example 1 capturedat a magnification of 10,000 times.

FIG. 10 is a SEM image of the transfer copy according to Example 1captured at a magnification of 60,000 times.

FIG. 11 is a SEM image of a transfer copy according to ComparativeExample 1 captured at a magnification of 60,000 times.

DESCRIPTION OF EMBODIMENTS

Hereinafter, (a) preferred embodiment(s) of the present invention willbe described in detail with reference to the appended drawings. Notethat, in this specification and the appended drawings, structuralelements that have substantially the same function and structure aredenoted with the same reference numerals, and repeated explanation ofthese structural elements is omitted.

1. Master

First, referring to FIG. 1 , an overview of a master according to anembodiment of the present invention will be described. FIG. 1 is aschematic perspective view of the master according to the presentembodiment.

As illustrated in FIG. 1 , a master 1 according to the presentembodiment includes, for example, a substrate 10 having a concave-convexstructure 12 on its outer peripheral surface.

The master 1 is, for example, a master used in roll-to-roll imprinting.In roll-to-roll imprinting, the outer peripheral surface of the master 1is pressed against the sheet-shaped substrate or the like as the master1 rotates, whereby the concave-convex structure on the outer peripheralsurface can be transferred to a sheet-shaped substrate or the like. Theuse of such imprinting enables efficient production of a large-areatransfer copy to which the concave-convex structure 12 on the outerperipheral surface of the master 1 has been transferred.

The transfer copy to which the concave-convex structure 12 has beentransferred by using the master 1 may be used as, for example, anoptical member such as a surface plasmon filter, a light-emittingdevice, or an anti-reflection film.

The substrate 10 is, for example, a member with a hollow cylindricalshape or cylindrical shape. The substrate 10 may have a hollowcylindrical shape with a hollow inside as illustrated in FIG. 1 , or mayhave a solid cylindrical shape without a hollow inside. The substrate 10may include a glass material such as fused quartz glass or syntheticquartz glass, or may include, for example, a metal such as stainlesssteel, or such a metal with the outer peripheral surface coated withSiO₂ or the like.

However, the substrate 10 preferably includes a glass material at leaston the outer peripheral surface and more preferably entirely includes aglass material such as quartz glass. This is because, in the case wherethe substrate 10 includes a glass material mainly including SiO₂, theconcave-convex structure 12 can be easily formed on the outer peripheralsurface of the substrate 10 by etching using a fluorine compound.Specifically, the concave-convex structure 12 can be easily formed onthe substrate 10 by forming a pattern corresponding to theconcave-convex structure 12 in a resist layer on the outer peripheralsurface of the substrate 10 by using laser lithography, and thenperforming dry etching using the resist layer as a mask.

The size of the substrate 10 is not limited. For example, the length ofthe substrate 10 in the axial direction may be 100 mm or more, and theouter diameter may be 50 mm or more and 300 mm or less. In the casewhere the substrate 10 has a hollow cylindrical shape, the thickness ofthe hollow cylinder may be 2 mm or more and 50 mm or less.

The concave-convex structure 12 is formed on the outer peripheralsurface of the substrate 10 and has continuously arranged concavities orconvexities. Specifically, in the concave-convex structure 12, theconcavities or convexities are continuously arranged at a predeterminedpitch in the circumferential direction of the substrate 10, and theconcavities or convexities are arranged with a predetermined phasedifference between circumferential rows adjacent in the axial directionof the substrate 10. In other words, the concavities or convexities inthe concave-convex structure 12 are out of phase with each other in theaxial direction of the substrate 10. The concavities or convexities arethus out of alignment with each other on a straight line parallel to theaxial direction of the substrate 10, but aligned with each other on astraight line at an angle to the axial direction of the substrate 10.

The concavities or convexities 121 refer to either convexities thatprotrude in the direction perpendicular to the outer peripheral surfaceof the substrate 10 or concavities that are concaved in the directionperpendicular to the outer peripheral surface of the substrate 10 and donot refer to a mixture of convexities and concavities in one master 1.

Referring to FIG. 2 , a specific structure of the concave-convexstructure 12 on the outer peripheral surface of the master according tothe present embodiment will be described here. FIG. 2 is a plan view ofan example of the concave-convex structure 12 on the outer peripheralsurface of the master according to the present embodiment. In FIG. 2 ,the direction X corresponds to the circumferential direction of thesubstrate 10, the direction Y corresponds to the axial direction of thesubstrate 10, and the direction Z corresponds to the directionperpendicular to the outer peripheral surface of the substrate 10.

As illustrated in FIG. 2 , the concave-convex structure 12 may be aconcave-convex structure with the concavities or convexities 121arranged in hexagonal lattice. In this case, the pitch between theconcavities or convexities 121 in the circumferential direction of thesubstrate 10 is also referred to as a dot pitch P_(D), and the intervalbetween the concavities or convexities 121 in circumferential rows (alsocalled tracks) adjacent in the axial direction of the substrate 10 isalso referred to as a track pitch P_(T).

In the concave-convex structure 12, the center positions of theconcavities or convexities 121 adjacent in the axial direction of thesubstrate 10 shift by ½P_(D) for each array (that is, track) of theconcavities or convexities 121 in the circumferential direction of thesubstrate 10. In other words, in the concave-convex structure 12, thephases of the concavities or convexities 121 shift by 180° betweenadjacent circumferential rows.

The dot pitch PD and the track pitch PT in the concave-convex structure12 may be, for example, less than 1 μm, preferably wavelengths or lessin the visible light region, and more preferably 100 nm or more and 350nm or less. In the case where the concave-convex structure 12 is a finestructure having such pitches, the concave-convex structure 12 canfunction as what is called a moth eye structure, which reducesreflection of incident light in a wide wavelength range.

However, if either the dot pitch PD or the track pitch PT is less than100 nm, it is difficult to form the concave-convex structure 12, whichis not preferred. If either the dot pitch PD or the track pitch PT ismore than 350 nm, diffraction of visible light occurs, and the functionas a moth eye structure is deteriorated, which is not preferred. As longas the dot pitch PD and the track pitch PT are in the foregoing range,the dot pitch PD and the track pitch PT may be the same or different.

The concave-convex structure 12 is not limited to hexagonal latticearrangement, and may have other arrangement. For example, theconcave-convex structure 12 may have the concavities or convexities 121arranged at the apexes and centers of squares. However, to most denselyarrange the concavities or convexities 121 on a plane, theconcave-convex structure 12 preferably has hexagonal lattice arrangementin which the concavities or convexities 121 are arranged at the apexesand centers of hexagons.

The concave-convex structure 12 has the concavities or convexities thatare continuously arranged without interruption. The concave-convexstructure 12 does not include a blank region where the concavities orconvexities are not formed in the axial direction of the substrate 10,or an error region where the arrangement of concavities or convexitiesis disordered. Specifically, the inside of the region with theconcave-convex structure 12 does not have a blank region where theconcavities or convexities are not formed in order to adjust the startposition of the exposure pattern, or an error region where thearrangement of the concavities or convexities is disordered due to theformation of a different pattern during exposure.

The transfer copy manufactured by using the master 1 having theconcave-convex structure 12 like this eliminates the need to selectregions with the concave-convex structure 12 before use, and alsoeliminates the need to discard regions other than the regions with theconcave-convex structure 12. Therefore, the master 1 according to thepresent embodiment enables more efficient mass production of thetransfer copy to which the concave-convex structure 12 has beentransferred.

2. Method for Manufacturing Master (2.1. Overview)

Next, a method for manufacturing the master 1 according to the presentembodiment will be described.

The master 1 according to the present embodiment is manufactured byforming a pattern corresponding to the concave-convex structure 12 onthe outer peripheral surface of the substrate 10 by using laser thermallithography, and then forming the concave-convex structure 12 on thesubstrate 10 by etching or the like. The arrangement of concavities orconvexities in the concave-convex structure 12 in the master 1 accordingto the present embodiment can be precisely controlled by forming thepattern corresponding to the concave-convex structure 12 by usinglithography with a laser beam whose irradiation position can becontrolled with high precision.

Here, anodizing is known as one of methods for forming a concave-convexstructure such as what is called a moth eye structure. Anodizinginvolves passing a current through an electrolyte solution, with analuminum substrate serving as an anode, which can simultaneously causedissolution and oxidation of the aluminum substrate and thus form aself-organized arrangement of cylindrical pores on the surface of thealuminum substrate.

However, in anodizing, the planar arrangement of concavities orconvexities depends on self-organization, which makes it difficult toform a given arrangement of concavities or convexities. In anodizing,the arrangement precision of the concavities or convexities is alsoaffected by the surface condition of the aluminum substrate and theuniformity of crystal grains, which makes it difficult to achievearrangement precision similar to that of the concave-convex structure 12of the master 1 according to the present embodiment. Furthermore, inanodizing, the concave-convex structure can be formed only on a metalsuch as aluminum that easily undergoes dissolution and oxidation in thepresence of an electric current in an electrolyte solution. In otherwords, not the use of anodizing, but the use of laser lithography aloneenables the master 1 according to the present embodiment to bemanufactured.

Specifically, the method for manufacturing the master 1 according to thepresent embodiment includes a depositing step of depositing a resistlayer on the outer peripheral surface of the substrate 10, an exposingstep of irradiating the resist layer with a laser beam to form a latentimage, a developing step of developing the resist layer with the latentimage to pattern the resist layer, and an etching step of performingetching with the patterned resist layer serving as a mask to form theconcave-convex structure 12 on the outer peripheral surface of thesubstrate 10.

In the depositing step, the resist layer is deposited on the outerperipheral surface of the substrate 10. The resist layer contains aninorganic material or organic material in which a latent image can beformed with a laser beam. As the inorganic material, a metal oxidecontaining, for example, one or two or more transition metals such astungsten or molybdenum can be used. The resist layer containing aninorganic material can be deposited by using, for example, sputtering.Meanwhile, as the organic material, for example, a novolak resist, achemically amplified resist or the like can be used. The resist layercontaining an organic material can be deposited by using spin coating orthe like.

In the exposing step, the resist layer on the outer peripheral surfaceof the substrate 10 is irradiated with a laser beam to form, in theresist layer, a latent image with a pattern corresponding to theconcave-convex structure 12. The wavelength of the laser beam with whichthe resist layer is irradiated is not limited, but may be a wavelengthin the blue light region from 400 nm to 500 nm.

In the developing step, the resist layer in which the latent image hasbeen formed by irradiation with the laser beam is developed to form thepattern corresponding to the latent image in the resist layer. Forexample, in the case where the resist layer contains the inorganicmaterial described above, the resist layer can be developed by using analkaline solution such as an aqueous solution of tetramethylammoniumhydroxide (TMAH). In the case where the resist layer contains theorganic material described above, the resist layer can be developed byusing an organic solvent such as an ester or an alcohol.

In the etching step, the substrate 10 is etched by using the patternedresist layer as a mask to form the concave-convex structure 12corresponding to the latent image on the outer peripheral surface of thesubstrate 10. The substrate 10 may be etched by either dry etching orwet etching. In the case where the substrate 10 includes a glassmaterial (e.g., quartz glass) mainly including SiO₂, the substrate 10can be etched by dry etching with a fluorocarbon gas or wet etching withhydrofluoric acid or the like.

(2.2. Exposure Method)

Next, referring to FIG. 3 to FIG. 7 , an exposure method used in themethod for manufacturing the master 1 according to the presentembodiment will be described. FIG. 3 is a schematic view illustratingthe exposure method used in the method for manufacturing the master 1according to the present embodiment.

In the exposing step in the method for manufacturing the master 1according to the present embodiment, the exposure signal that controlsemission of the laser beam and the rotation control signal that controlsrotation of the substrate 10 share a reference clock. This enablesprecise control of the irradiation position of the laser beam on theouter peripheral surface of the substrate 10 and can thus improve thearrangement precision of the concave-convex structure 12 formed on theouter peripheral surface of the master 1.

As illustrated in FIG. 3 , the method for manufacturing the master 1according to the present embodiment involves, for example, forming anexposure pattern 12A on the outer peripheral surface of the substrate 10by irradiating the substrate 10 with a laser beam 30 using an exposureapparatus 3 including a laser source 31, which emits the laser beam 30,and a control mechanism 47, which controls emission of the laser beam30.

The laser source 31 emits the laser beam 30. The laser source 31 may be,for example, a semiconductor laser source. The wavelength of the laserbeam 30 emitted by the laser source 31 is not limited, but may be, forexample, a wavelength in the blue light region from 400 nm to 500 nm.

The control mechanism 47 generates the exposure signal that controlsemission of the laser beam 30. The control mechanism 47 may be, forexample, a function generator including a signal generating circuit thatcan generate a signal with a given waveform.

In the exposure apparatus 3, the exposure pattern 12A is formed on theouter peripheral surface of the substrate 10, which has a hollowcylindrical shape or cylindrical shape and rotates about its centralaxis, upon irradiation of the outer peripheral surface of the substrate10 with the laser beam 30 while performing scanning along the axialdirection (the direction indicated by arrow R in FIG. 3 ) of thesubstrate 10. Accordingly, the exposure apparatus 3 enables spiralirradiation of the outer peripheral surface of the substrate 10 with thelaser beam and can thus form the exposure pattern 12A in desired regionson the outer peripheral surface of the substrate 10.

Since the circumference of the substrate 10 may change for each rotationdue to the machining error of the substrate 10, failed synchronizationbetween the exposure signal and the rotation control signal disordersthe arrangement of the exposure pattern as the exposure progresses. Inaddition, since the rotation speed of the spindle motor of a turn tablefor rotating the substrate 10 fluctuates, the fluctuation in rotationspeed disorders the arrangement of the exposure pattern.

Therefore, the synchronization between the exposure signal and therotation control signal has conventionally prevented or reducedarrangement disorder of the exposure pattern for each rotation. In thiscase, however, the frequency of the exposure signal is limited to thedivided or multiplied frequency of the rotation control signal. It isthus difficult to synchronize the exposure signal and the rotationcontrol signal in forming an exposure pattern with an arrangement inwhich the pitch is shifted for each rotation, such as hexagonal latticearrangement.

It has thus been studied that the exposure pattern of hexagonal latticearrangement is formed by, for example, inverting the phase of theexposure signal for each rotation or adjusting the exposure start timingfor each rotation by using a start pulse (also called Z phase signal)generated, at regular timing for each rotation, from the spindle motorof the turn table for rotating the substrate 10. However, in this case,a blank region where no exposure pattern is formed or an error regionwhere the exposure pattern deviates from a desired pattern is generatedfor each rotation, which impairs the continuity of the exposure pattern.

In the method for manufacturing the master 1 according to the presentembodiment, the exposure signal and the rotation control signal share areference clock serving as a reference for signal generation, so thatthe exposure signal and the rotation control signal are insynchronization with each other. According to this feature, thefrequency of the exposure signal is not limited to the divided ormultiplied frequency of the rotation control signal and can be set to agiven value. According to the method for manufacturing the master 1according to the present embodiment, a continuous exposure pattern withgiven arrangement can thus be formed on the outer peripheral surface ofthe substrate 10 while the continuity of the exposure signal ismaintained. According to the method for manufacturing the master 1according to the present embodiment, the continuous concave-convexstructure 12 in which the concavities or convexities are arranged withhigh precision without interruption, pattern disorder, or the like canthus be formed on the outer peripheral surface of the master 1.

Referring to FIG. 4 , the correspondence relationship between theexposure signal generated by the control mechanism 47 and the exposurepattern 12A formed on the outer peripheral surface of the substrate 10will be specifically described here. FIG. 4 is an explanatory viewillustrating the correspondence relationship between the exposure signaland the exposure pattern.

As illustrated in FIG. 4 , in the case where the exposure pattern withcircular dots arranged in hexagonal lattice is formed on the outerperipheral surface of the substrate 10, the exposure apparatus 3 mayuse, as the exposure signal, for example, a pulse wave whose amplituderepeatedly alternately reaches high level and low level at predeterminedperiods. At this time, the exposure apparatus 3 may control emission ofthe laser beam 30 so as to form an exposure pattern on the outerperipheral surface of the substrate 10 when the amplitude of theexposure signal reaches high level.

To arrange circular dots in hexagonal lattice in the exposure pattern,it is important to precisely control the arrangement of the exposurepattern formed on the outer peripheral surface of the substrate 10. Forexample, the circular dots can be arranged in hexagonal lattice bysetting the frequency of the rotation control signal and the exposuresignal, which controls irradiation with the laser beam 30, such that theexposure signal shifts by ½ pulses between circumferential rows adjacentin the axial direction of the substrate 10.

Referring to FIG. 5 , the correspondence relationship between therotation control signal and the exposure signal in the case of formingthe hexagonal lattice exposure pattern as illustrated in FIG. 4 will bespecifically described. FIG. 5 is an explanatory view illustrating thecorrespondence relationship between the exposure signal and the rotationcontrol signal.

In order to invert the phase of the exposure signal by 180° for eachrotation while the signal continuity of the exposure signal and therotation control signal is maintained, it is important that the exposuresignal generates a number of pulses including a fractional part of 0.5,not an integer number of pulses, while the rotation control signalgenerates an integer number of pulses corresponding to one rotation. Thespindle motor of the turn table is controlled so as to make one rotationwhen the rotation control signal inputs a predetermined number ofpulses. When the number of pulses of the exposure signal includes afractional part of 0.5, the phase in the n-th rotation and the (n+2)-throtation can thus be shifted by 180° with respect to the phase in the(n+1)-th rotation.

Accordingly, the number of pulses of the exposure signal is controlledto include a fractional part of 0.5, while the number of pulses of therotation control signal corresponding to one rotation is controlled tobe an integer. As a result, the phase of the exposure signal can beinverted by 180° for each rotation. It is thus possible to form ahexagonal lattice exposure pattern in which circular dots are staggeredin circumferential rows adjacent in the axial direction of the substrate10.

(2.3. Signal Generation Method)

Next, referring to FIG. 6 , a method for generating the exposure signaland the rotation control signal described above will be described. FIG.6 is a block diagram illustrating the mechanism for generating theexposure signal and the rotation control signal.

As illustrated in FIG. 6 , a waveform generating device 450, whichgenerates a rotation control signal, has a reference clock generatingsection 400 built therein. The reference clock generated by thereference clock generating section 400 is supplied to a formatter 48,which generates an exposure signal. The exposure signal generated by theformatter 48 is inputted into a driver 49 and used to control emissionof the laser beam 30 from the laser source 31. The rotation controlsignal generated by the waveform generating device 450 is inputted intoa spindle motor 45 and used to control rotation of the spindle motor 45of a turn table for rotating the substrate 10.

The reference clock generating section 400 generates a pulse wave with apredetermined frequency, which serves as a reference clock. Thegenerated reference clock is supplied to a first signal generatingsection 410 in the formatter 48 and a second signal generating section420 in the waveform generating device 450.

The first signal generating section 410 is included in the formatter 48and performs signal processing on the supplied reference clock togenerate an exposure signal. Specifically, the first signal generatingsection 410 generates an exposure signal by changing the frequency ofthe reference clock so as to form a desired exposure pattern andcontrolling the duty cycle of the pulse wave in consideration of theoutput of the laser source 31 and the properties of the resist layer.

The second signal generating section 420 is included in the waveformgenerating device 450 and performs signal processing on the suppliedreference clock to generate a rotation control signal. Specifically, thesecond signal generating section 420 generates a rotation control signalby changing the frequency of the reference clock such that the spindlemotor 45 of the turn table rotates at a desired rotation speed.

Here, in the case of exposing the hexagonal lattice array pattern, thefrequency of the exposure signal generated by the first signalgenerating section 410 is not an integral multiple of the frequency ofthe rotation control signal generated by the second signal generatingsection 420. This is because the frequency is set such that the exposuresignal generates a number of pulses including a fractional part of 0.5while the rotation control signal generates an integer number of pulses.Thus, the exposure signal and the rotation control signal cannot begenerated in the same signal generating circuit, but are generated inseparate signal generating circuits as illustrated in FIG. 6 . Since thefrequency of the exposure signal is not an integral multiple of thefrequency of the rotation control signal but the exposure signal and therotation control signal are generated in signal generating circuits thatshare a reference clock, the exposure signal and the rotation controlsignal are in synchronization with each other.

Although FIG. 6 illustrates a configuration where the reference clockgenerating section 400 is located in the waveform generating device 450,the present invention is not limited to this configuration. For example,the spindle motor 45 of the turn table also has a signal generatingcircuit built therein, and thus an output signal in synchronization withthe rotation control signal can be extracted from the spindle motor 45.This output signal may thus be used to generate an exposure signal. Evenin such a case, the exposure signal in synchronization with the rotationcontrol signal can be obtained.

(2.4. Configuration of Exposure Apparatus)

Next, referring to FIG. 7 , a specific configuration of the exposureapparatus 3 which performs exposure of the substrate 10 with a hollowcylindrical shape or cylindrical shape by using the exposure signal andthe rotation control signal generated by the configuration illustratedin FIG. 6 will be described. FIG. 7 is a block diagram describing aspecific configuration of the exposure apparatus 3 used in exposure ofthe substrate 10.

As illustrated in FIG. 7 , the exposure apparatus 3 includes the lasersource 31, a first mirror 33, a photodiode (PD) 34, a condenser lens 36,an electro-optic deflector (EOD) 39, a collimator lens 38, a secondmirror 41, a beam expander (BEX) 43, and an objective lens 44.

The laser source 31 is controlled by the exposure signal generated bythe control mechanism 47. The laser beam 30 emitted from the lasersource 31 is applied to the substrate 10 placed on a turn table 46. Theturn table 46 on which the substrate 10 is placed rotates with thespindle motor 45 controlled by the rotation control signal generated bythe waveform generating device 450. Here, since the common referenceclock is supplied to the formatter 48 and the waveform generating device450, the exposure signal and the rotation control signal are insynchronization with each other.

The laser source 31 emits the laser beam 30 to which the resist layerdeposited on the outer peripheral surface of the substrate 10 is to beexposed, as described above. The laser source 31 may be, for example, asemiconductor laser source that emits a laser beam with a wavelength inthe blue light region from 400 nm to 500 nm. The laser beam 30 emittedfrom the laser source 31 travels straight as it is a collimated beam.The laser beam 30 is reflected by the first mirror 33.

The laser beam 30 reflected by the first mirror 33 is condensed onto theelectro-optic deflector 39 through the condenser lens 36 and thenconverted into a collimated beam through the collimator lens 38 again.The collimated laser beam 30 is reflected by the second mirror 41 andhorizontally directed to a beam expander 43.

The first mirror 33 includes a polarization beam splitter and has afunction of reflecting one of polarization components and transmittingthe other polarization component. The polarization component that haspassed through the first mirror 33 is photoelectrically converted by thephotodiode 34, and the photoelectrically converted received light signalis inputted into the laser source 31. As a result, for example, theoutput of the laser beam 30 from the laser source 31 can be adjusted onthe basis of the feedback from the inputted received light signal.

The electro-optic deflector 39 can control the irradiation position ofthe laser beam 30 with approximately nanometer-scale precision. In theexposure apparatus 3, the irradiation position of the laser beam 30applied to the substrate 10 can be finely adjusted with theelectro-optic deflector 39.

The beam expander 43 forms the laser beam 30 directed by the secondmirror 41 into a desired beam shape. The laser beam 30 is applied to theresist layer deposited on the outer peripheral surface of the substrate10 through the objective lens 44.

The turn table 46 supports the substrate 10. The turn table 46 rotatesthe substrate 10 as the turn table 46 is rotated by the spindle motor45. Since the turn table 46 can cause the irradiation position of thelaser beam 30 to move in the axial direction of the substrate 10 (thatis, the direction indicated by arrow R) while rotating the substrate 10,the outer peripheral surface of the substrate 10 can be spirallyexposed. The irradiation position of the laser beam 30 may be moved bymoving, along a slider, either a laser head including the laser source31 or the turn table 46 that supports the substrate 10.

The control mechanism 47 includes the formatter 48 and the driver 49 andcontrols emission of the laser beam 30 from the laser source 31 tocontrol the irradiation time and the irradiation position of the laserbeam 30.

The driver 49 controls emission of the laser beam 30 from the lasersource 31 on the basis of the exposure signal generated by the formatter48. Specifically, the driver 49 may control the laser source 31 suchthat the outer peripheral surface of the substrate 10 is irradiated withthe laser beam 30 when the amplitude of the exposure signal reaches highlevel. The spindle motor 45 rotates the turn table 46 on the basis ofthe rotation control signal generated by the waveform generating device450. Specifically, the spindle motor 45 may control rotation such thatthe turn table 46 makes one rotation when the rotation control signalinputs a predetermined number of pulses.

The exposure apparatus 3 as described above enables formation of anexposure pattern on the substrate 10. The exposure apparatus 3 enablesprecise formation of the exposure pattern with given arrangement on theouter peripheral surface of the substrate 10.

The substrate 10 exposed by the exposure apparatus 3 undergoes thedeveloping step and the etching step as described above, which forms theconcave-convex structure 12 on the outer peripheral surface of thesubstrate 10. The master 1 according to the present embodiment ismanufactured accordingly.

3. Usage Example of Master

Next, referring to FIG. 8 , a method for efficiently manufacturing atransfer copy by using the master 1 according to the present embodimentwill be described. Specifically, a transfer copy to which theconcave-convex structure 12 on the outer peripheral surface of themaster 1 has been transferred can be continuously manufactured by usinga transfer apparatus 5 illustrated in FIG. 8 . FIG. 8 is a schematicview illustrating the configuration of the transfer apparatus 5 formanufacturing a transfer copy by using the master 1 according to thepresent embodiment.

As illustrated in FIG. 8 , the transfer apparatus 5 includes the master1, a substrate supply roll 51, a winding roll 52, guide rolls 53 and 54,a nip roll 55, a release roll 56, a coating device 57, and a lightsource 58. In other words, the transfer apparatus 5 illustrated in FIG.8 is a roll-to-roll imprint transfer apparatus.

The substrate supply roll 51 is, for example, a roll around which asheet-shaped substrate 61 is wound in a rolled manner. The winding roll52 is a roll around which a transfer copy is wound. The transfer copyhas a resin layer 62 laminated thereon, and the concave-convex structure12 has been transferred to the resin layer 62. The guide rolls 53 and 54convey the sheet-shaped substrate 61 before and after transfer. The niproll 55 presses the sheet-shaped substrate 61 having the resin layer 62laminated thereon against the master 1. The release roll 56 releases thesheet-shaped substrate 61 on which the resin layer 62 is laminated fromthe master 1 after the concave-convex structure 12 is transferred to theresin layer 62.

The coating device 57 includes a coating means such as a coater, andapplies a photocurable resin composition to the sheet-shaped substrate61 to form the resin layer 62. The coating device 57 may be, forexample, a gravure coater, a wire bar coater, or a die coater. The lightsource 58 emits light having a wavelength with which a photocurableresin composition can be cured. The light source 58 may be, for example,an ultraviolet lamp.

The photocurable resin composition is cured when irradiated with lighthaving a predetermined wavelength. Specifically, the photocurable resincomposition may be an ultraviolet curable resin such as acrylic resinacrylate and epoxy acrylate. If necessary, the photocurable resincomposition may contain an initiator, a filler, a functional additive, asolvent, an inorganic material, a pigment, an antistatic agent, or asensitizing dye.

The resin layer 62 may include a thermosetting resin composition. Insuch a case, the transfer apparatus 5 includes a heater instead of thelight source 58. The heater heats the resin layer 62, and the resinlayer 62 is hereby cured, whereby the concave-convex structure 12 istransferred. The thermosetting resin composition may be, for example, aphenolic resin, an epoxy resin, a melamine resin, or a urea resin.

In the transfer apparatus 5, the sheet-shaped substrate 61 is firstcontinuously fed from the substrate supply roll 51 through the guideroll 53. The photocurable resin composition is applied to the fedsheet-shaped substrate 61 by the coating device 57, so that the resinlayer 62 is laminated on the sheet-shaped substrate 61. The sheet-shapedsubstrate 61 having the resin layer 62 laminated thereon is pressedagainst the master 1 by the nip roll 55. The concave-convex structure 12formed on the outer peripheral surface of the master 1 is transferred tothe resin layer 62 accordingly. The resin layer 62 to which theconcave-convex structure 12 has been transferred is cured by irradiationwith light from the light source 58. The inverted structure of theconcave-convex structure 12 is formed in the resin layer 62 accordingly.The sheet-shaped substrate 61 to which the concave-convex structure 12has been transferred is released from the master 1 by the release roll56, fed to the winding roll 52 through the guide roll 54, and woundaround the winding roll 52.

The transfer apparatus 5 like this can efficiently and continuouslymanufacture the transfer copy to which the concave-convex structure 12on the outer peripheral surface of the master 1 has been transferred.

EXAMPLES

The master according to the present embodiment will be more specificallydescribed below with reference to Example and Comparative Examples.Example described below is an example of the conditions for illustratingthe operability and the effects of the master and the method formanufacturing the master according to the present embodiment. The masterand the method for manufacturing the master according to the presentinvention are not limited to the following Example.

Example 1

A master according to Example 1 was manufactured through the followingsteps. First, a resist layer of about 50 nm to 60 nm including amaterial containing a tungsten oxide was sputtered on the outerperipheral surface of a hollow cylindrical substrate (axial length 480mm×outer diameter 140 mm) including quartz glass. Next, a latent imagewas formed in the resist layer by performing laser thermal lithographyusing the exposure apparatus as illustrated in FIG. 7 . A 10 MHz pulsesignal with 50% duty cycle was used as a reference clock, and anexposure signal and a rotation control signal were each generated on thebasis of the reference clock.

For example, the number of pulses corresponding to one rotation of aspindle motor (corresponding to the number of counts for one rotation ofa rotary encoder that controls the spindle motor) is 4096 pulses. Whenthe substrate 10 is rotated at 900 rpm, the frequency of the rotationcontrol signal is 61.44 kHz (4096×900/60=61440).

The circumference of the hollow cylindrical substrate having an outerdiameter of 140 mm is about 440 mm. Therefore, for example, in the caseof forming a hexagonal lattice exposure pattern with circular dotsarranged at a pitch of about 270 nm, the number of the dots along thecircumference is 1628973.5. Therefore, the frequency of the exposuresignal is 24.4346025 MHz (1628973.5×900/60=24434602.5) when thesubstrate 10 is rotated at 900 rpm.

Further, to form a hexagonal lattice with circular dots at a dot pitchof 270 nm, the interval (track pitch) between circumferential rowsadjacent in the axial direction of the substrate is about 234 nm. Tomake spiral exposure at an interval of about 234 nm, the turn table andthe irradiation position of a laser beam are thus moved at a relativespeed of 3.51 μm/sec (234×900/60=3510).

The outer peripheral surface of the substrate was irradiated with andexposed to the laser beam while the irradiation position of the laserbeam was moved at 3.51 μm/sec in the axial direction of the substrate byusing the exposure signal with a frequency of 24.4346025 MHz and therotation control signal with a frequency of 61.44 kHz (50% duty cyclefor both signals).

Next, the substrate after exposure was subjected to developmentprocessing with NMD3 (2.38 mass % aqueous solution oftetramethylammonium hydroxide) (available from Tokyo Ohka Kogyo Co.,Ltd.), whereby the resist in the latent image parts was dissolved toform a dot array concave-convex structure in the resist layer. Next, thesubstrate was etched for 60 to 120 minutes by performing reactive ionetching (RIE) with a CHF₃ gas (30 sccm) at a gas pressure of 0.5 Pa andan input power of 200 W using, as a mask, the resist layer obtainedafter development. The remaining resist layer was then removed.

The master having the concave-convex structure on its outer peripheralsurface was manufactured through the above-described steps. A transfercopy was further manufactured by using the manufactured master.Specifically, a transfer copy according to Example 1 was manufactured bytransferring the concave-convex structure on the outer peripheralsurface of the master to an ultraviolet curable resin by using thetransfer apparatus illustrated in FIG. 8 . As the sheet-shaped substrateof the transfer copy, a polyethylene terephthalate film was used. Theultraviolet curable resin was cured by irradiation with ultraviolet raysfrom a metal halide lamp at 1000 mJ/cm² for 1 minute.

Comparative Example 1

A master and a transfer copy were manufactured by a method similar tothat of Example 1 except that the exposure signal and the rotationcontrol signal did not share a reference clock, and the exposure signal(24.576 MHz) in synchronization with the rotation control signal wasgenerated by multiplying the frequency (61.44 kHz) of the rotationcontrol signal by 400. In Comparative Example 1, the phase of theexposure signal was inverted by 180° for each rotation on the basis of astart pulse generated one time at regular timing per rotation in orderto form a hexagonal lattice exposure pattern.

Comparative Example 2

A master and a transfer copy were manufactured by a method similar tothat of Example 1 except that the exposure signal and the rotationcontrol signal did not share a reference clock, and the exposure signal(24.576 MHz) in synchronization with the rotation control signal wasgenerated by multiplying the frequency (61.44 kHz) of the rotationcontrol signal by 400. In Comparative Example 2, the output timing ofthe exposure signal was controlled by measuring the number of pulsesfrom a start pulse, which was generated one time at regular timing perrotation, for each rotation on the basis of the start pulse in order toform a hexagonal lattice exposure pattern.

Evaluation Results

The images obtained by observing the transfer receiving bodiesmanufactured by using the masters according to Example 1 and ComparativeExample 1 and captured at a magnification of 10,000 times or 60,000times with a scanning electron microscope (SEM) are shown in FIG. 9 toFIG. 11 . FIG. 9 is a SEM image of the transfer copy according toExample 1 captured at a magnification of 10,000 times. FIG. 10 is a SEMimage of the transfer copy according to Example 1 captured at amagnification of 60,000 times. FIG. 11 is a SEM image of the transfercopy according to Comparative Example 1 captured at a magnification of60,000 times.

In FIG. 9 to FIG. 11 , the direction X corresponds to thecircumferential direction of the substrate, the direction Y correspondsto the axial direction of the substrate, and the direction Z correspondsto the direction perpendicular to the outer peripheral surface of thesubstrate. FIG. 10 and FIG. 11 are images of the concave-convexstructure in a region exposed upon generation of the start pulse.

FIG. 9 indicates that the master and the transfer copy according toExample 1 do not have, for example, a blank region where theconcave-convex structure is not formed, or an error region where thepattern is disordered, but have a concave-convex structure whereconvexities are continuously arranged in a hexagonal lattice.

The comparison between FIG. 10 and FIG. 11 indicates that the transfercopy according to Comparative Example 1 has convexities arranged in ahexagonal lattice but has an error region where the pattern arrangementis disordered. In Comparative Example 1, the exposure signal is reset atthe timing of start pulse generation to invert the phase, and theexposure pattern in a region exposed during that time thus deviates froma desired pattern. Meanwhile, it is indicated that the transfer copyaccording to Example 1 does not have an error region with a disorderedpattern, but has a continuous pattern because the exposure signal is notsubjected to resetting or the like at the timing of start pulsegeneration.

The SEM observation result of the transfer copy according to ComparativeExample 2, although not shown, was substantially similar to that ofComparative Example 1. Specifically, the transfer copy according toComparative Example 2 has convexities arranged in a hexagonal lattice,but has a blank region where no pattern is formed. This is because, inComparative Example 2, the start position of the exposure signal iscontrolled by measuring the number of pulses at the timing of startpulse generation, and no exposure pattern is thus formed in a regionduring that time.

According to an embodiment of the present invention as described above,there can be provided a master having a continuously formedconcave-convex structure. The master does not have a blank region whereconcavities or convexities are not formed in the axial direction of thesubstrate or an error region where the arrangement of concavities orconvexities is disordered. Therefore, according to an embodiment of thepresent invention, there can be provided a master that offers improvedmass production and a method for manufacturing the master. The massproductivity of the transfer copy manufactured by using the masteraccording to the present embodiment can also be improved.

The preferred embodiment(s) of the present invention has/have beendescribed above with reference to the accompanying drawings, whilst thepresent invention is not limited to the above examples. A person skilledin the art may find various alterations and modifications within thescope of the appended claims, and it should be understood that they willnaturally come under the technical scope of the present invention.

REFERENCE SIGNS LIST

1 master3 exposure apparatus5 transfer apparatus10 substrate12 concave-convex structure30 laser beam31 laser source45 spindle motor47 control mechanism48 formatter49 driver121 concavities or convexities400 reference clock generating section410 first signal generating section420 second signal generating section450 waveform generating device

1. A master comprising: a substrate with a hollow cylindrical shape orcylindrical shape; and a concave-convex structure on an outer peripheralsurface of the substrate, wherein the concave-convex structure hasconcavities or convexities continuously arranged in a spiral shape in acircumferential direction of the substrate at a dot pitch equal to orless than a wavelength of a visible light band, and the concavities orconvexities are arranged with a predetermined phase difference betweencircumferential rows adjacent in an axial direction of the substrate. 2.The master according to claim 1, wherein the concave-convex structuredoes not have a blank region where the concavities or convexities arenot formed in the axial direction of the substrate.
 3. The masteraccording to claim 2, wherein the concave-convex structure has theconcavities or convexities continuously and uninterruptedly arranged inthe spiral shape on the outer peripheral surface of the substrate at thedot pitch, such that the concave-convex structure does not have theblank region for each round of the spiral arrangement.
 4. The masteraccording to claim 1, wherein the concave-convex structure does not havea blank region where the concavities or convexities are not formed inthe axial direction of the substrate, or an error region whereconcavities or convexities are formed in an arrangement different fromthe arrangement of the concavities or convexities.
 5. The masteraccording to claim 4, wherein the concave-convex structure has theconcavities or convexities continuously and uninterruptedly arranged inthe spiral shape on the outer peripheral surface of the substrate at thedot pitch, such that the concave-convex structure does not have theblank region or the error region for each round of the spiralarrangement.
 6. The master according to according to claim 1, whereinthe concave-convex structure has the concavities or convexities arrangedin a hexagonal lattice at the dot pitch and a track pitch equal to orless than the wavelength of the visible light band on the outerperipheral surface of the substrate.
 7. The master according toaccording to claim 6, wherein the dot pitch and the track pitch areequal to or more than 100 nm and equal to or less than 350 nm.
 8. Themaster according to according to claim 1, wherein at least the outerperipheral surface of the substrate includes a glass material.
 9. Atransfer copy obtained by transferring a concave-convex structure on anouter peripheral surface of the master according to claim 1 to asheet-shaped substrate with the master.